Heterostructures of BaTiO₃ bilayer films grown on SrTiO ₃ (0 0 1) under different oxygen pressures

BaTiO₃ bilayer films are deposited on SrTiO₃ substrates under different oxygen pressures by pulsed laser deposition. The structural properties of the bilayers are investigated by means of X-ray diffraction, Rutherford backscattering spectrometry, conventional and high-resolution transmission electron microscopy. The BaTiO₃ layer with the thickness of 115 nm deposited under higher oxygen pressure (3×10^-1mbar) exhibits a cubic-like structure with lattice parameter a=0.399nm. The BaTiO₃ layer with the thickness of 220 nm deposited under lower oxygen pressure (2×10^-3 mbar) shows a c-axis-oriented domain structure with lattice parameters a=0.401nm and c=0.411nm. The interface of the BaTiO₃ bilayer films is coherent and no interfacial dislocations can be seen over larger regions. The misfit dislocations with Burgers vector of type a〈1 0 0〉 are observed at the interface between bottom BaTiO₃ layer and SrTiO₃ substrates.